# NPM Symbol Export Verifier

> NPM Symbol Export Verifier is a paid API for AI agents from 401-chi.vercel.app, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-16).

Checks whether a named symbol is publicly exported by a specific npm package version, returning existence, export kind, and certainty level.

## Facts

- Endpoint: POST https://401-chi.vercel.app/api/v1/symbol
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/npm-symbol-export-verifier-2678afab
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_5pMnBj8m2aGlxAsCdGFi5

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability npm-symbol-export-verifier-2678afab -d '<json body>'
```

Example prompt: Can you verify whether the symbol `createStore` is a named export in the npm package `redux` at version 4.2.0?

## When to prefer this

Use this endpoint when you need to programmatically verify that a specific named symbol (function, class, type, constant) is publicly exported by a pinned npm package version before generating code, validating dependency compatibility, or auditing API surface changes across versions. It is preferable over manual registry inspection or documentation lookups when certainty and structured evidence are required by an automated agent workflow.

## Known failure modes

- Package version not found on npm registry — returns inconclusive certainty or error
- Symbol does not match identifier pattern (must start with letter, $, or _) — validation error
- Invalid semver version string — rejected by input schema
- Package name does not conform to npm naming rules — schema validation failure
- Ecosystem value other than 'npm' — rejected (only npm supported)
- Network or registry fetch failure — may return inconclusive certainty with partial evidence

## How this service works

Verify whether a named API symbol is publicly exported by an exact npm package version. Returns structured existence, export kind, certainty, and package-artifact evidence.

## Output

Returns a structured JSON object with a query echo (ecosystem, package, requestedVersion, symbol), a result block (exists: boolean, exportKind: named/default/namespace/type/unknown/null, certainty: verified/inconclusive), an evidence array with source artifacts and package version details, and a retrievedAt timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "symbol": {
   "type": "string",
   "pattern": "^[A-Za-z_$][A-Za-z0-9_$]*$",
   "maxLength": 512,
   "minLength": 1
  },
  "package": {
   "type": "string",
   "pattern": "^(?:@[a-z0-9][a-z0-9._-]*\\/)?[a-z0-9][a-z0-9._-]*$",
   "maxLength": 214,
   "minLength": 1
  },
  "version": {
   "type": "string",
   "pattern": "^v?\\d+\\.\\d+\\.\\d+(?:-[0-9A-Za-z-]+(?:\\.[0-9A-Za-z-]+)*)?(?:\\+[0-9A-Za-z-]+(?:\\.[0-9A-Za-z-]+)*)?$",
   "maxLength": 100,
   "minLength": 1
  },
  "ecosystem": {
   "type": "string",
   "const": "npm"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/npm-symbol-export-verifier-2678afab/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 401-chi.vercel.app](https://www.zero.xyz/host/401-chi.vercel.app/llms.txt)